Advancements in semiconductor technology have led to the production of large scale integrated circuits which have brought about a revolution in the electronics industry. Microelectronic components are now widely used in the production of a variety of electronic devices (i.e. computers, calculators, watches). Development of such miniature electronic instruments has demanded the evolution of batteries as miniature power supplies. This new generation of batteries must produce higher energy per unit volume and superior discharge characteristics as compared to traditional batteries.
Miniature batteries based on aqueous, non-aqueous and solid electrolytes are manufactured as power sources for microelectronic and portable electronic equipment. As an example, thin solid state batteries are often constructed with an anode formed of solid lithium, or an alloy of lithium, and a cathode constructed of a solid electrolyte. This type of battery has a long shelf life and operates efficiently over a wide temperature range.
These thin solid state batteries employ a polymeric electrolyte containing a suitable inorganic ion salt interposed between the cathode and the anode. Electrochemical cells containing a polymeric matrix may suffer from low ion conductivity and, accordingly, in order to maximize the conductivity of these materials, the matrix is generally constructed into a very thin film, i.e., on the order of about 25 to about 250 .mu.m. As is apparent, the reduced thickness of the film reduces the total amount of internal resistance within the electrolyte thereby minimizing losses in conductivity due to internal resistance.
The majority, if not the totality, of lithium batteries under development use intercalation compounds as preferred cathode materials. The lithium-intercalation compound combination benefits from high cyclability, but suffers from sloping charge and discharge voltage profiles. What is desired is a high energy density battery with a constant discharge voltage that can be used, for example, in instrumentation and computer memory backup.
Accordingly, it is an object of the present invention to provide a thin film lithium polymer battery having a flat discharge curve.
It is another object of the present invention to provide a novel cathode material for thin film lithium polymer batteries.
Other objects and advantages of the present invention will be apparent to those skilled in the art.